PALEOZOIC GROUP. 303 



south of Burnet a succession of beds occurs which is equivalent to the Deep 

 Creek division, and this is underlaid by the Hoover division of the Leon 

 series, with very few, if any, of the Hinton Beds. The base of the former 

 there, as elsewhere, so far as now known, is always a gritty fine-grained dol- 

 omite, here assumed as the lowest member of the highest Silurian division. 



B. DEEP CREEK DIVISION (HUDSON ? OR NIAGARAN ?). 



Deep Creek and its branches, especially in the lower stretches, exhibit a 

 peculiar topography of a type characteristic of the massive terrane which 

 crowns the Silurian system in Central Texas. 



This is, par excellence, the siliceous division of the Paleozoic in our district, 

 the beds being solid masses of cherty limestones mingled with gritty dolo- 

 mites and tough magnesian limestone, the last often containing abundant 

 segregated semi-geodes of drusy quartz. The distribution of the Deep Creek 

 strata is as unique and interesting as the texture and composition. Reference 

 has already been made to the ancient shore line of the Hinton age which 

 followed along the southern edge of San Saba County, with a southward 

 prolongation or bay extending down into western Llano County and another 

 into western Burnet County. The representative of the American Trenton? 

 Sea had a somewhat different coast in this region. In Burnet County part of 

 the Hinton land surface became depressed so as to allow deposition over a 

 considerable portion of that area during the succeeding age. The western 

 bay in Llano County retreated northward but slightly, although the shore- 

 line in San Saba County and further west was apparently pushed out north- 

 ward in places and extended back southward in others. 



Long faults, which can be traced in some instances for many miles, and 

 subsequent denudation to an even grade, have left the field in very bad shape 

 for rapid study. Much remains to be done in piecing out gaps in the record 

 but the section given below is so often repeated that it may be regarded as a 

 fair presentation of the succession of strata. In ascending order there are: 



1. A stratum of gritty, fine-grained, saccharoidal, light grey, or slightly 

 yellowish, highly siliceous dolomite, weathering dark grey. Included in this, 

 or above it, are similar but tougher dolomites, with numerous scattered 

 patches of drusy quartz following surfaces of a somewhat regular, crumpled, 

 or molded pattern. The forms and disposition of these infiltrations, although 

 they are disconnected, suggests the possibility of a connection with organic 

 growth. But as yet they have not been studied minutely. The thickness, 

 all told, is about 50 feet. 



2. Strata of dolomite gradually becoming tough and cherty, and weather- 

 ing with deeply pitted surfaces. Thickness in places 40 feet. These contain 

 cherty (fossiliferous?) nodules, small, weathering "in relief;" above which, in 

 sections removed from the old shore line, are often 



